1. Field of the Invention
The present invention relates to a temperature compensating dielectric ceramic composition, and laminated ceramic parts such as a laminated ceramic condenser and a laminated LC filter, each of which is formed by using such a temperature compensating dielectric ceramic composition.
2. Description of the Related Art
Conventionally, a temperature compensating ceramic condenser has been used as one of widely used electronic parts in various electronic devices in order to effect desired turning, oscillating and the like. Meanwhile, it has been demanded that the temperature compensating ceramic condenser be made compact in size, its dielectric loss should be small and its dielectric property be stable. As dielectric ceramic parts capable of satisfying the above requirements, it has been demanded that they should have a large relative dielectric constant and a small dielectric loss (namely, a large Q value) although its size is required to be small.
As such a desired dielectric ceramic mentioned above, there has been suggested a series of BaO--TiO.sub.2 dielectric ceramic composition (H. M. O'Brayan, J. Am, Ceram. Soc. 57(1974) 450; Japanese Examined Patent Publication 58-20905). Although a laminated ceramic condenser formed by using these dielectric ceramic compositions has been in actual use, since the sintering temperature involved in the manufacturing of such a product is as high as 1300 to 1400.degree. C., its internal electrode has to be made by a noble metal such as palladium (Pd) and platinum (Pt) capable of resisting such high temperature.
As some dielectric ceramic compositions which can be sintered at a relatively low temperature during their manufacturing processes, Japanese Unexamined Patent Publication No. 8-239262 has suggested a dielectric ceramic composition containing BaO--TiO.sub.2 --Nd.sub.2 O.sub.3 as its main component and a PbO--V.sub.2 O5--B.sub.2 O.sub.3 --SiO.sub.2 glass as an additive. For the same purpose, Japanese Unexamined Patent Publication No. 9-71462 has disclosed another dielectric ceramic composition containing BaO--TiO.sub.2 --Nd.sub.2 O.sub.3 --Sm.sub.2 O.sub.3 as its main component and also containing an additive which is a PbO--ZnO--B.sub.2 O.sub.3 glass having a softening point of 500.degree. C. or lower.
Since it is desired to let the dielectric ceramic compositions disclosed in Japanese Unexamined Patent Publication No. 8-239262 and Japanese Unexamined Patent Publication No. 9-71462 be sintered at a relatively low temperature during their manufacturing processes, each of the dielectric ceramic composition is formed by incorporating a glass which contains a Pb oxide component. Since the Pb oxide component has a high volatility during the process of manufacturing the glass and in a process of sintering the ceramic, the Pb oxide content will be different from lot to lot or even different in different portions of the same lot. As a result, there has been a problem that the properties of thus obtained ceramic are not stable.